1515 College AvenueManhattan, KS 66502

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Frank Arthur received his Ph.D. in Entomology from North Carolina State University in December 1985. He joined the staff of the Stored Product Insects Research and Development Laboratory at Savannah, GA in March 1986, and was transferred to the Center for Grain and Animal Health Research upon closure of the Savannah Laboratory in November 1994. He is responsible for developing applied research programs for insect pest management in stored cereal grains and processed food warehouses. Previous studies have included pesticide degradation on stored commodities, residual efficacy of insecticides applied to different substrates, evaluation of new chemicals for use in post-harvest environments, and expanded use of aeration to control insect pests in stored grains. Current research interests are the development of aeration management strategies for crops stored in different geographic regions, evaluation of microbial pathogens for use in raw grains or on surface substrates, identification of physical and environmental factors that affect the efficacy of residual insecticides, and simulated field studies involving chemical and non-chemical controls. Research projects often involve cooperative efforts with private industry, other entomologists at the Manhattan laboratory, research and extension entomologists at various state universities, and biologists associated with the U. S. Military.

Current Research Projects

Insect Pest Management for Flour Mills: Residual Efficacy of Aerosols With the impending phase-out of the fumigant Methyl Bromide, the wheat industry is expanding the use of aerosol insecticides for insect pest management in milling facilities. Combinations of pyrethrin combined with the insect growth regulator (IGR) methoprene (Diacon II®) are often used to control the red flour beetle (RFB) and the confused flour beetle (CFB), two common stored-product pest insects in wheat mills throughout the USA. Insect growth regulators affect molting and development of immature insects, but generally do not kill adults, hence they are often combined with an insecticide that will kill adults.

Even though the RFB and CFB are similar in size and appearance they usually vary in susceptibility to insecticides. There is little information on how long the residues from an aerosol application will give control of either of these two important pest species. We placed wheat flour or one of seven packaging materials inside a flour mill, and then exposed these materials to commercial aerosol formulations containing either 1% or 3% pyrethrin with the same amount of Diacon II®. We removed the treated flour and packaging materials and held them for 16 weeks in the laboratory. Every two weeks for 16 weeks, we put larvae of each species on different sets of the exposed flour and the exposed packaging materials (with flour), and then determined if larvae could reach the adult stage.

Both formulations gave complete control of RFB on the flour and on the packaging materials for 16 weeks, but the formulations were less effective against the CFB because more CFB larvae were able to reach the adult stage compared to the RFB. Increasing the pyrethrin concentration from 1% to 3% did lead to a reduction in the number of CFB adults, indicating that there may have been an interaction between the pyrethrin and the Diacon II® components of the formulation. However, the residual efficacy is largely due to the presence of the IGR. In addition, results from other studies with Diacon II® used as a residual surface treatment, and results of studies with the IGRs hydroprene (Gentrol®) and pyriproxyfen (NyGuard®), indicate that the RFB is more susceptible than the CFB. Since both the RFB and CFB can infest flour mills, species identification is important when IGRs are being used for insect control.

Directional Flow of Aeration to Manage Insect Pests in Stored WheatUsing low-volume ambient air to cool stored grain is a common management practice in the southern plains, but little research has been done recently to determine if the direction of airflow makes a difference regarding the cooling and insect pest populations. We conducted a 2-year study at the USDA ARS Center for Grain and Animal Health Research (CGAHR), using 1,000 bushel metal storage bins filled with wheat. We evaluated suction aeration, pulling air downward through the grain mass, as compared to pressure aeration, the standard strategy of pushing cool air upward through the grain mass. Results were consistent each of the two years and showed that temperatures on the upper surface of the grain mass were consistently cooler with suction aeration than with pressure aeration. The resulting insect pest populations were also generally lower in the bins with suction versus pressure aeration. Our results indicated that using suction aeration would cool the upper surface zone of the grain mass, which is vulnerable to insect infestation, and could reduce the need for additional pesticide inputs through this reduction in pest pressure.

The results of the previous study are promising and warrant further investigation in larger bins. A new study has been initiated to examine temperature gradients in the headspace zone of wheat storage bins with pressure versus suction aeration, and to determine the extent of the interactions between the headspace temperatures and those in the upper surface zone of the bulk grain mass. Studies are being conducted at the CGAHR, this time using 4,000 bushel bins. The first year has been completed, and results are similar to the earlier study in that more insects are found in the bins with pressure aeration compared to the bins with suction aeration. Headspace temperature patterns are different with the two aeration methods, and even with the larger bins the surface zone of the wheat appears to be cooler with suction aeration compared to pressure aeration.

Several beetle species can be major pests of stored food products, but there are few studies where resident populations have been monitored for more than one year in commercial facilities. We monitored beetle populations a food warehouse for three years using attractants. The focal points of infestation shifted during the storage period, but beetles were found even in areas of the warehouse where no food products were stored. Specific sites were identified where beetles were most prevalent. Actual numbers of beetles fluctuated depending on the amount and location of goods in the warehouse, and also show that the movement of goods into and out of the warehouse also affected insect populations. Results show how targeted monitoring of insect pests can aid in making management decisions, while taking into account the dynamic nature of insect infestations inside active commercial facilities.

Evaluation of synergized pyrethrin aerosol for control of Tribolium castaneum and Tribolium confusum (Coleptera: Tenebrionidae)

Aerosol insecticides are used to control flour beetles in milling facilities, and there are areas within flour mills where food spillage can accumulate and provide harborage sites for insect infestations. There is a need for information regarding the effect of food material on aerosol effectiveness. When the insects were directly exposed to the aerosol, mortality was high, but when they were exposed with flour, or exposed in the treated flour, mortality was greatly reduced. Larvae of both species were less susceptible to the pyrethrin aerosol in the presence of flour compared to adults and pupae, possibly because they were able to burrow into the flour and escape exposure. Results of this study show that sanitation and cleaning in conjunction with aerosol application may yield increased control of flour beetle populations in milling and food storage facilities.

The Indianmeal moth is a major pest of stored food products, but there are few studies where resident populations have been monitored for more than one year in commercial facilities. We monitored Indianmeal moth populations inside a food warehouse for three years using an attractant for male moths. The focal points of infestation shifted during the storage period, but moths were consistently trapped in certain locations. Also, we caught moths in traps that were in places where no food was stored. In general, more moths were caught during the summer months compared to the remainder of the year. Cost estimates for the monitoring program were calculated using values provided by private industry. We used these values to show how reducing the number of traps could provide information on infestation trends while lowering the costs associated with insect monitoring. Results show the importance of monitoring for Indianmeal moths, but also emphasize the dynamic nature of insect infestations inside an active warehouse.

Susceptibility of stored-product psocids to aerosol insecticides

Psocids (insects which are also called booklice) are pests of stored grains and grain products in most of the world, and they have natural tolerance to some of the insecticides used for control of other stored-product insect pests, such as beetles and moths. Aerosol insecticides are used in flour mills and warehouses to control beetle and moth pests, but their effect on psocids pests needs to be determined. We evaluated two commonly used aerosol insecticides, methoprene and esfenvalerate, applied alone and in combination for control of four species of stored-product psocid pests. The greatest mortality of psocids attained was 76% for immature psocids and 62% for adult psocids, indicating that the aerosols did not provide effective control of the tested psocid species. This study shows that psocids may be tolerant to these aerosol insecticides when applied at rates that are normally effective for control of other stored-product insect pests. This information will help pest managers choose appropriate control strategies for psocid pests.

Efficacy of Aerosols for Managing the Red Flour Beetle

Pest management professionals commonly utilize aerosolized liquid applications, also known as fogging, for management of stored-product insects including the red flour beetle.These applications are part of a potential methyl bromide replacement technology because they may increase the time interval between structural fumigations or heat treatments. The objectives of this study were to examine influence of flour accumulation, exposure location, life stage, and insecticide on the efficacy of aerosol applications. Data show that aerosolized insecticide applications in dishes without food residues placed in the open produced the highest red flour beetle mortality. Conversely, mortality significantly decreased with food and exposure under pallets. Poster

Fontenot, E.A., F.H. Arthur, J.R. Nechols, and M.R. Langemeier. 2013. Economic feasibility of methoprene applied as a surface treatment and as an aerosol alone and in combination with two other insecticides. J. Econ. Entomol. 106: 1503-1510.